Given the choice between gas and electric I would go gas, but as ElFenix states a wood burner with an offset firebox is the best way to go.
Smoking can be expensive as it takes 12-18 hours and that can use a ton of engergy.
My rules for smoking
1. Cut your own wood, if you have to buy your own grillwood or use charcoal, gas or electric it gets crazy expensive
2. When you fire up the smoker load it as full as possible, couple of briskets, several racks of ribs, 4 or 5 chickens, etc.... Spending the time and energy for a single brisket or a couple of racks of ribs is terribly inefficient
Cutting your own wood isn't really practical. You have to let the wood sit for 6 months to a year to dry out completely. You also need to remove the bark as that will give a bitter taste. You should be able to buy fruitwood from an orchard for $5/bunch. That's what I do. 5 or so bunches gives me enough to cook with for the summer.
This is the best starter smoker:
http://www.amazon.com/Char-Griller-2.../dp/B0009NAE5Y
I've had mine for TEN YEARS now, and only requires a coat of grill paint once a year. I added the
firebox option for the side as well. I've since made my own barrel smoker, but still use this for small jobs.
The main things you need to know are:
1) Never use direct heat. Think like cooking in an oven.
2) Keep the inside moist (that's what sh....) Keep a can of apple juice or water inside the smoker to keep the meat from drying out.
3) Wait for your coals to get ready. It takes 30-45 minutes. Never put your meat in when there's smoke billowing off of your coals. The coals should be white and glowing.
4) I like to mix lump charcoal and fruitwood. Wood on it's own doesn't last long and you have to keep adding it. Lump charcoal gets pretty hot and lasts longer, but doesn't affect the flavor.
5) Keep your heat regulated to around 250-300F. You'll use ventilation to regulate this. This is why a good chimney is important.
6) You can soak some wood chips and add a handful to the coals once in a while if you want more intense smoke flavor. This works well with hickory and mesquite.
Other than that, it's just a waiting game. I know everyone has their own marinades, rubs, etc, but that's all personal taste. As far as cooking goes, my main recommendation is wrap the meat loosely in foil to prevent an overwhelming smoke flavor. You can uncover it once it forms a "skin". It's mostly "set it and forget it." though. I have a huge yard, so on Sundays in the summer I'll pop some pork shoulders, loins, beef ribs, or a couple of chickens in the barrel, do my lawn, and in a few hours it's ready to go.
If you do it right, you should have a nice pink smoke ring around the outer edge of the meat when it's done:
Here's some of my handywork from last year:
And here's my family's sauce of choice:
Enjoy.